For expository convenience, the present application refers to the present invention as a Realizer.TM. system, the lexicon being devoid of a succinct descriptive name for a system of the type hereinafter described.
The Realizer system comprises hardware and software that turns representations of large digital logic networks into temporary actual operating hardware form, for the purpose of simulation, prototyping, execution or computing. (A digital logic network is considered "large" when it is contains too many logic functions to be contained in a few of the largest available configurable logic devices.)
The following discussions will be made clearer by a brief review the relevant terminology as it is typically (but not exclusively) used.
To "realize" something is to make it real or actual. To realize all or part of a digital logic network or design is to cause it to take actual operating form without building it permanently.
An "input design" is the representation of the digital logic network which is to be realized. It contains primitives representing combinational logic and storage, as well as instrumentation devices or user-supplied actual devices, and nets representing connections among primitive input and output pins.
To "configure" a logic chip or interconnect chip is to cause its internal logic functions and/or interconnections to be arranged in a particular way. To configure a Realizer system for an input design is to cause its internal logic functions and interconnections to be arranged according to the input design.
To "convert" a design is to convert its representation into a file of configuration data, which, when used directly to configure Realizer hardware, will cause the design to be realized.
To "operate" a design is to cause Realizer hardware, which is configured according to the input design's representations, to actually operate.
An "interconnect" is a reconfigurable means for passing logic signals between a large number of chip I/O pins as if the pins were interconnected with wires.
A "path" is one of the built-in interconnection wires between a logic chip and a crossbar chip in a partial crossbar interconnect, or between crossbar chips in a hierarchy of partial crossbars.
A "path number" specifies a particular path, out of the many that may interconnect a pair of chips.
An "ERCGA" is an electronically reconfigurable gate array, that is a collection of combinational logic, and input/output connections (and optionally storage) whose functions and interconnections can be configured and reconfigured many times over, purely by applying electronic signals.
A "logic chip" is an ERCGA used to realize the combinational logic, stroage and interconnections of an input design in the Realizer system.
An "Lchip" is a logic chip, or a memory module or user-supplied device module which is installed in place of a logic chip.
An "interconnect chip" is an electronically reconfigurable device which can implement arbitrary interconnections among its I/O pins.
A "routing chip" is an interconnect chip used in a direct or channel-routing interconnect.
A "crossbar chip" is an interconnect chip used in a crossbar or partial crossbar interconnect.
An "Xchip" is a crossbar chip in the partial crossbar which interconnects Lchips. A "Ychip" is a crossbar chip in the second level of a hierarchical partial crossbar interconnect, which interconnects Xchips. A "Zchip" is a crossbar chip in the third level of a hierarchical partial crossbar interconnect, which interconnects Ychips.
A "logic board" is a printed circuit board carrying logic and interconnect chips. A "box" is a physical enclosure, such as a cardcage, containing one or more logic boards. A "rack" is a physical enclosure containing one or more boxes.
A "system-level interconnect" is one which interconnects devices larger than individual chips, such as logic boards, boxes, racks and so forth.
A "Logic Cell Array" or "LCA" is a particular example of ERCGA which is manufactured by Xilinx, Inc., and others and is used in the preferred embodiment.
A "configurable logic block" or "CLB" is a small block of configurable logic and flip-flops, which represent the combinational logic and storage in an LCA.
A "design memory" is a memory device which realizes a memory function specified in the input design.
A "vector memory" is a memory device used to provide a large body of stimulus signals to and/or collect a large body of response signals from a realized design in the Realizer system.
A "simulator" is a device in the Realizer system used to provide stimulus signals to an individual input of a realized design. A "sampler" is a device in the Realizer system used to collect response signals from an individual output of a realized design.
A "host computer" is a conventional computer system to which the Realizer system's host interface hardware is connected, and which controls the configuration and operation of the Realizer hardware.
An "EDA system" is a electronic design automation system, that is a system of computer-based tools used for creating, editing and analyzing electronic designs. The host EDA system is the one which generates the input design file in most Realizer system applications.
If a reconfigurable gate array with enough capacity to hold a single large design were available, then much of the Realizer technology would be unnecessary. However, this will never be the case, for two reasons.
First, ERCGAs cannot have as much logic capacity as a non-reconfigurable integrated circuit of the same physical size made with the same fabrication technology. The facilities for reconfigurability take up substantial space on the chip. An ERCGA must have switching transistors to direct signals and storage transistors to control those switches, where a non-reconfigurable chip just has a metal trace, and can put those transistors to use as logic. The regularity required for a reconfigurable chip also means that some resources will go unused in real designs, since placement and routing of regular logic structures are never able to use 100% of the available gates. These factors combine to make ERCGAs have about one tenth the logic capacity of non-reconfigurable chips. In actual current practice, the highest gate capacity claimed for an ERCGA is 9,000 gates (Xilinx XC3090). Actual semi-custom integrated circuits fabricated with similar technology offer over 100,000 gate logic capacity (Motorola).
Second, it is well known that real digital systems are built with many integrated circuits, typically ten to one hundred or more, often on many printed circuit boards. If an ERCGA did have as much logic capacity as the largest integrated circuit, it would still take many such chips to realize most digital systems. Since it does not, still more are required.
Consequently, for a Realizer system to have the logic capacity of even a single large-scale chip, it should have many ERCGAs, on the order of ten. To have the capacity for a system of such chips, on the order of hundreds of ERCGAs are required. Note that this is true regardless of the specific fabrication capabilities. If a fabrication process can double the capacity of ERCGAs by doubling the number of transistors per chip, then non-reconfigurable chip capacities and therefore overall design sizes will double, as well.
For these reasons, to build a useful Realizer system, it is necessary to be able to interconnect hundreds of ERCGAs in an electronically reconfigurable way, and to convert designs into configurations for hundreds of ERCGAs. This invention does not cover the technology of any ERCGA itself, only the techniques for building a Realizer system out of many ERCGAs.
ERCGA technology does not show how to build a Realizer system, because the problems are different. ERCGA technology for reconfigurably interconnecting logic elements which are all part of one IC chip does not apply to interconnecting many. ERCGA interconnections are made simply by switching transistors that pass signals in either direction. Since there are no barriers across one chip, there are a large number of paths available for interconnections to take. Since the chip is small, signal delays are small. Interconnecting many ERCGAs is a different problem, because IC package pins and printed circuit boards are involved. The limited number of pins available means a limited number of paths for interconnections. Sending signals onto and off of chips must be done through active (i.e. amplifying) pin buffers, which can only send signals in one direction. These buffers and the circuit board traces add delays which are an order of magnitude greater than the on-chip delays. The Realizer system's interconnection technology solves these problems in a very different way than the ERCGA.
Finally, the need to convert a design into configurations for many chips is not addressed by ERCGA technology. The Realizer system's interconnect is entirely different than that inside an ERCGA, and an entirely different method of determining and configuring the interconnect is required.
ERCGAs are made with the fastest and densest silicon technology available at any given time. (1989 Xilinx XC3000 LCAs are made in 1 micron SRAM technology.) That is the same technology as the fastest and densest systems to be realized. Because ERCGAs are general and have reconfigurable interconnections, they will always be a certain factor less dense than contemporary gate arrays and custom chips. Realizer systems repeat the support for generality and reconfigurability above the ERCGA level. Therefore, a Realizer system is always a certain factor, roughly one order of magnitude, less dense than the densest contemporary systems. Board-level Realizer systems realize gate arrays, box-level Realizer systems realize boards and large custom chips, and rack-level Realizer systems realize boxes.
Design architectures are strongly affected by the realities of packaging. I/O pin width: at the VLSI chip level, 100 I/O pins is easily built, 200 pins are larger but not uncommon, and 400 pins is almost unheard of. At the board level, these figures roughly double. Logic densities: boards often accommodate 5 VLSI chips, 10 is possible, and 20 is unusual, simply because practical boards are limited to about 200 square inches maximum. Boxes accommodate 10 to 20 boards, rarely 40. Interconnect densities: modules may be richly interconnected on chips and boards, as several planes of two-dimensional wiring are available, but less so at the box level and above, as backplanes are essentially one-dimensional.
These packaging restrictions have a strong effect on system architectures that should be observed in effective Realizer systems. Because of the lower density in a Realizer system, a single logic chip will usually be realizing only a module in the realized design. A one-board logic chip complex will be realizing a VLSI chip or two, a box of Realizer boards will realize a single board in the design, and a rack of boxes will realize the design's box of boards.
Thus, a Realizer system's board-level logic and interconnect complex needs to have as much logic and interconnect capacity and I/O pin width as the design's VLSI chip. The Realizer system's box needs as much as the design's board, and the Realizer system's rack needs as much as the design's box.